CHBC · California Historical Building Code
Combustion air and venting requirements for fuel‑burning appliances
For historic California buildings the CHBC requires fuel‑burning appliances to have a sufficient supply of combustion air and to be vented to the outdoors via approved vents; masonry chimneys can remain if inspected and documented as sound, while terra cotta and certain metal vents in concealed spaces generally require mitigation and approval.
Last reviewed: July 6, 2026
What the code requires — plain English
All fuel‑burning appliances in a qualified historical building must have a sufficient supply of combustion air for safe combustion, ventilation and draft‑hood dilution — CHBC § 8-902.5.
Every appliance that must be vented must be tied to an approved venting system that produces a positive flow to carry combustion products outside — CHBC § 8-902.6.
Existing masonry chimneys may remain in use if the flue and masonry are evaluated and documented as sound; terra cotta chimneys and Type C metallic vents in concealed spaces cannot remain in use unless mitigated and approved case‑by‑case — CHBC § 8-902.6.2.
The single most important rule: fuel‑burning appliances must be given enough air to burn cleanly and must vent combustion products to the outdoors using approved venting — document and test existing historic chimneys before relying on them.
Requirements in detail
High‑level duties (what the CHBC actually requires)
- Provide a sufficient supply of air for each fuel‑burning appliance for proper combustion, ventilation and draft‑hood dilution (CHBC § 8-902.5).
- Connect every appliance that is required to be vented to an approved venting system; the venting must develop a positive flow adequate to convey combustion products outdoors (CHBC § 8-902.6.1, part of § 8-902.6).
- Existing masonry chimneys may remain if evaluated and documented that masonry and grout are in good condition; terra cotta chimneys and Type C metallic vents in concealed spaces are not automatically acceptable (CHBC § 8-902.6.2).
- The enforcing agency may require operational testing where systems do not comply with the regular code (CHBC § 8-902.5.2, § 8-902.6.3).
Note: The CHBC applies these mechanical rules in conjunction with the regular code — mechanical systems “shall comply with the regular code unless otherwise modified by this chapter” (CHBC § 8-902.1). For technical sizing and detailed methods (for example, combustion‑air opening sizing), the regular code (California Mechanical/Plumbing Code) contains the quantitative procedures.
Decision‑relevant dimensions and values (what you need to check)
| Decision factor | What CHBC requires | Code Reference |
|---|---|---|
| What air is required | Sufficient supply of air for proper combustion, ventilation, and draft‑hood dilution — CHBC requires sufficiency, not the numeric method. | § 8-902.5 |
| Enforcement/testing | Enforcing agency may require operational tests when systems do not comply with regular code. | § 8-902.5.2 |
| Vent connection | Every appliance required to be vented must be connected to an approved venting system that develops positive flow to the outside. | § 8-902.6.1 (part of § 8-902.6) |
| Existing masonry chimneys | Masonry chimneys in structurally sound condition may remain — requires flue evaluation and documentation of masonry/grout condition. | § 8-902.6.2 |
| Terra cotta / Type C in concealed spaces | Not permitted to remain in concealed spaces unless mitigated and approved case‑by‑case. | § 8-902.6.2 |
| Operational testing for vents | Enforcing agency may require operational tests for venting systems not complying with regular code. | § 8-902.6.3 |
What CHBC does not spell out (and where to go next)
- The CHBC states the performance requirement (sufficiency, approved venting, inspections) but does not publish the numeric sizing methods or specific opening dimensions. For numeric sizing and detailed installation methods, consult the regular California Mechanical or Plumbing Code (e.g., chapter on combustion air and Appendix J examples) and appliance manufacturer instructions; the CHBC expects compliance with the regular code unless specifically modified.
Exceptions & special cases
- The enforcing agency may accept alternative solutions that achieve equivalent life safety (CHBC § 8-902.1.3). Use this when retaining historic fabric would otherwise force noncompliance; document equivalence.
- Existing systems that the enforcing agency determines do not constitute a safety hazard may remain in use (CHBC § 8-902.1.2). This is a site‑specific determination; it does not remove the agency’s authority to require tests or mitigation under §§ 8-902.5.2 / 8-902.6.3.
- Masonry chimneys: may remain only after an evaluation and documentation that masonry and grout are in good condition (CHBC § 8-902.6.2). If that documentation cannot be provided, the chimney must be repaired, lined, or replaced to meet safety.
- Terra cotta chimneys and Type C metallic vents located in concealed spaces are treated as unacceptable to remain by default unless a mitigation strategy is prepared and approved on a case‑by‑case basis (CHBC § 8-902.6.2).
Common mistakes
- Assuming an old chimney is automatically acceptable without documented inspection. CHBC requires evaluation/documentation for masonry chimneys ( § 8-902.6.2 ).
- Relying on terra cotta or Type C vents in concealed cavities without mitigation and enforcing‑agency approval ( § 8-902.6.2 ).
- Focusing only on appliance replacement and neglecting the venting connection: every vent‑required appliance must be connected to an approved venting system that produces positive flow to the outside ( § 8-902.6.1 ).
- Treating CHBC as containing the sizing tables — CHBC gives the performance and conditional allowances; for numeric sizing follow the regular code (mechanical/plumbing) or the appliance manufacturer’s instructions. The CHBC explicitly expects mechanical systems to comply with the regular code unless modified ( § 8-902.1 ).
- Not coordinating with the enforcing agency when proposing to retain historic venting systems. The enforcing agency may require operational testing and can approve alternatives ( §§ 8-902.5.2, 8-902.6.3, 8-902.1.3 ).
Worked example — how to apply the CHBC in a real situation (with numbers shown from the regular code example)
Important framing: CHBC requires a sufficient supply of combustion air but does not give the numeric sizing method in the CHBC text. The numeric method below is taken from the regular plumbing/mechanical code example and is provided to show how to meet the CHBC requirement in practice. See the CHBC direction to follow the regular code ( § 8-902.1 ) and the CHBC combustion‑air/venting rules ( §§ 8-902.5, 8-902.6, 8-902.6.2 ).
Scenario
- Basement appliances: a fan‑assisted furnace rated 100,000 Btu/h and a draft‑hood water heater rated 40,000 Btu/h. Basement dimensions: 15 ft × 30 ft × 8 ft ceiling → volume 3,600 cu ft.
Application
- CHBC requires sufficient combustion air ( § 8-902.5 ). To determine if the existing space is sufficient, apply the standard sizing method in the regular code (example taken from the California Plumbing Code Appendix J): the typical method uses 50 cu ft per 1,000 Btu/h of appliance input. Using that method: total input = 140,000 Btu/h → required room volume = 140 × 50 = 7,000 cu ft. (Example and calculation method from the Plumbing Code Appendix J.)
- Compare volumes: available = 3,600 cu ft; required = 7,000 cu ft → insufficient. Under CHBC, you cannot rely on the room alone to provide “sufficient supply of air” ( § 8-902.5 ).
- Next steps to comply with the CHBC requirement: provide combustion air from outdoors or combination indoor/outdoor openings sized per the regular code procedures (Plumbing/Mechanical Code) and/or use listed direct‑vent appliances. If you intend to rely on an existing masonry chimney for venting, document its condition first ( § 8-902.6.2 ).
Why this example is allowed under the CHBC: The CHBC sets the safety requirement (sufficient air and approved venting) and expects the project to apply regular‑code sizing and manufacturer instructions to meet it (CHBC § 8-902.1).
Related CHBC provisions
- CHBC § 8-902.1 — Mechanical systems follow the regular code unless modified; agency may accept alternatives.
- CHBC § 8-902.1.2 — Existing systems that do not constitute a safety hazard may remain in use (agency determination).
- CHBC § 8-902.1.3 — Enforcing agency may approve alternatives achieving equivalent life safety.
- CHBC § 8-902.5.2 — Enforcing agency may require operational tests for combustion‑air systems.
- CHBC § 8-902.6.1 — Appliances that require venting must be connected to an approved venting system with positive flow.
- CHBC § 8-902.6.3 — Enforcing agency may require operational tests for venting systems.
- CHBC § 8-902.7 — Ducts: existing duct systems that do not create hazards may remain in use.
- CHBC § 8-902.9 — Miscellaneous equipment requirements (appliances must be installed so no safety hazard is created).
Code references
Grounded in the retrieved California Historical Building Code — click a citation to read the verbatim passage:
CHBC § 8-901.5 High relevance — show source text
8-901.5 Energy conservation. Qualified historical buildings or properties covered by this part are exempted from compliance with energy conservation standards. When new nonhistorical lighting and space conditioning system components, devices, appliances and equipment are installed, they shall comply with the requirements of Title 24, Part 6, The California Energy Code, except where the historical significance or character-defining features are threatened.
SECTION 8-902 — MECHANICAL
8-902.1 General. Mechanical systems shall comply with the regular code unless otherwise modified by this chapter.
8-902.1.1 The provisions of the CHBC shall apply to the acceptance, location, installation, alteration, repair, relocation, replacement or addition of any heating, ventilating, air conditioning, domestic incinerators, kilns or miscellaneous heat-producing appliances or equipment within or attached to a historical building.
8-902.1.2 Existing systems which do not, in the opinion of the enforcing agency, constitute a safety hazard may remain in use.
8-902.1.3 The enforcing agency may approve any alternative to the CHBC which would achieve equivalent life safety.
8-902.2 Heating facilities. All dwelling-type occupancies covered under this chapter shall be provided with heating facilities. Woodburning or pellet stoves or fireplaces may be acceptable as heating facilities.
8-902.3 Fuel oil piping and tanks. Fuel oil piping and tanks shall comply with regular code requirements except that the enforcing agency may waive such requirements where the lack of compliance does not create a safety or environmental hazard.
8-902.4 Heat-producing and cooling equipment. Heat-producing and cooling equipment shall comply with the regular code requirements governing equipment safety, except that the enforcing agency may accept alternatives which do not create a safety hazard.
8-902.5 Combustion air.
8-902.5.1 All fuel-burning appliances and equipment shall be provided a sufficient supply of air for proper fuel combustion, ventilation and draft hood dilution.
8-902.5.2 The enforcing agency may require operational tests for combustion air systems which do not comply with applicable requirements of the regular code.
8-902.6 Venting of appliances.
8-902.6.1 Every appliance required to be vented shall be connected to an approved venting system. Venting systems shall develop a positive flow adequate to convey all combustion products to the outside atmosphere.
8-902.6.2 Masonry chimneys in structurally sound condition may remain in use for all fuel-burning appliances, provided the flue is evaluated and documentation provided that the masonry and grout are in good condition. Terra cotta chimneys and Type C metallic vents installed in concealed spaces shall not remain in use unless otherwise mitigated and approved on a case-by-case basis.
8-902.6.3 The enforcing agency may require operational tests for venting systems which do not comply with applicable requirements of the regular code.
8-902.7 Ducts.
8-902.7.1 New ducts shall be constructed and installed in accordance with applicable requirements of the regular code.
8-902.7.2 Existing duct systems which do not comply with applicable requirements of the regular code and do not, in the opinion of the enforcing agency, constitute a safety or health hazard may remain in use.
8-902.8 Ventilating systems.
2025 CALIFORNIA HISTORICAL BUILDING CODE 19
CMC § 2025 High relevance — show source text
Systems that carry nonabrasive exhaust, such as smoke, moderate abrasives such as sawdust, and high abrasives such as manganese or acid vapors use product-conveying ducts. Part II provides the minimum fire safety requirements related to the design, installation, inspection, and maintenance of grease-type operations, such as cooking, for both fuel-gas and solid fuel. Cooking produces a significant amount of smoke, fumes, vapors, heat, and other pollutants. Therefore, acceptable kitchen ventilation is necessary to prevent fires from the build-up of grease and to provide the occupants protection from smoke, unpleasant odors, pollutants, and dangerous gases. There are two types of exhaust hoods (Type I and Type II) used in commercial kitchen applications.
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FORMAT OF THE UNIFORM MECHANICAL CODE
Type I hoods are intended to be installed above equipment or appliances that generate grease or smoke. Type II hoods are intended to be installed above equipment or appliances that generate steam, vapor, heat, or odors and do not generate grease or smoke.
Chapter 6 Duct Systems. Chapter 6 regulates requirements for ducts and plenums that are portions of a heating, cooling, ventilation, or exhaust system. This chapter contains material and installation requirements for metal, gypsum, factory-made, flexible, and plastic ducts. It also contains provisions for duct insulation, dampers, fire protection, and automatic shutoff for the building’s air distribution system. It is worth noting that exhaust ducts are regulated by Chapter 5, and combustion air ducts are regulated by Chapter 7.
Chapter 7 Combustion Air. Chapter 7 regulates combustion air requirements for ventilation and dilution of flue gases for appliances installed in buildings. Fuel-gas appliances not regulated by chapter include direct vent appliances and Type I clothes dryers. Makeup air requirements for Type I clothes dryers are located in Chapter 5. Chapter 7 provides acceptable methods for supplying satisfactory combustion air to ensure proper combustion. Combustion air can be supplied by using indoor combustion air or by introducing the air from the outdoors.
Combustion is the rapid oxidation of fuel to release energy. The oxygen required to release the energy from the fuel normally comes from the air. Incomplete combustion of fuel occurs when inadequate oxygen is provided to the appliance. Combustion is needed to provide ventilation cooling for the casing and internal controls. When a lack of oxygen occurs, some of the carbon is not oxidized, and carbon monoxide forms.
Chapter 8 Chimneys and Vents. Chapter 8 regulates the installation, design, and construction of venting systems for fuel-burning appliances. The provisions addressed within this chapter follow procedures an installer would use to design or evaluate a venting system. Many requirements apply to the design and construction of venting systems, chimneys, installation of gas vents, and the sizing of venting system for a Category I appliance. Sizing venting systems require rigorous engineering calculations. However, the venting sizing requirements and sizing tables in this chapter already perform the calculations for the benefit of the end user.
Combustion appliances produce products of incomplete combustion, including potentially harmful carbon monoxide (CO). It is desirable to vent these products to the outdoors. Although the gas is clean-burning fuel, the products of combustion must not be allowed to collect within a building.
CHBC § 8-902.5 High relevance — show source text
8-902.5 Combustion air.
8-902.5.1 All fuel-burning appliances and equipment shall be provided a sufficient supply of air for proper fuel combustion, ventilation and draft hood dilution.
8-902.5.2 The enforcing agency may require operational tests for combustion air systems which do not comply with applicable requirements of the regular code.
8-902.6 Venting of appliances.
8-902.6.1 Every appliance required to be vented shall be connected to an approved venting system. Venting systems shall develop a positive flow adequate to convey all combustion products to the outside atmosphere.
8-902.6.2 Masonry chimneys in structurally sound condition may remain in use for all fuel-burning appliances, provided the flue is evaluated and documentation provided that the masonry and grout are in good condition. Terra cotta chimneys and Type C metallic vents installed in concealed spaces shall not remain in use unless otherwise mitigated and approved on a case-by-case basis.
8-902.6.3 The enforcing agency may require operational tests for venting systems which do not comply with applicable requirements of the regular code.
8-902.7 Ducts.
8-902.7.1 New ducts shall be constructed and installed in accordance with applicable requirements of the regular code.
8-902.7.2 Existing duct systems which do not comply with applicable requirements of the regular code and do not, in the opinion of the enforcing agency, constitute a safety or health hazard may remain in use.
8-902.8 Ventilating systems.
2025 CALIFORNIA HISTORICAL BUILDING CODE 19
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
MECHANICAL, PLUMBING AND ELECTRICAL REQUIREMENTS
8-902.8.1 Ventilating systems shall be installed so that no safety hazard is created.
8-902.8.2 Grease hoods and grease hood exhaust systems shall be furnished and installed in accordance with applicable requirements of the regular code. Existing systems which are altered shall comply with the regular code.
8-902.9 Miscellaneous equipment requirements.
8-902.9.1 The following appliances and equipment shall be installed so that no safety hazard is created: warm air furnaces, space heating equipment, vented decorative appliances, floor furnaces, vented wall furnaces, unit heaters, room heaters, absorption units, refrigeration equipment, duct furnaces, infrared radiant heaters, domestic incinerators, miscellaneous heat-producing appliances and water heaters.
8-902.9.2 Storage-type water heaters shall be equipped with a temperature- and pressure-relief valve in accordance with applicable requirements of the regular code.
SECTION 8-903 — PLUMBING
8-903.1 General. Plumbing systems shall comply with the regular code unless otherwise noted.
8-903.1.1 The provisions of the CHBC shall apply to the acceptance, location, installation, alteration, repair, relocation, replacement or addition of any plumbing system or equipment within or attached to a historical building.
8-903.1.2 Existing systems which do not, in the opinion of the enforcing agency, constitute a safety hazard may remain in use.
8-903.1.3 The enforcing agency may approve any alternative to these regulations which achieves reasonably equivalent life safety.
8-903.2 Residential occupancies.
CMC § 2025 High relevance — show source text
Chapter 7 Combustion Air. Chapter 7 regulates combustion air requirements for ventilation and dilution of flue gases for appliances installed in buildings. Fuel-gas appliances not regulated by chapter include direct vent appliances and Type I clothes dryers. Makeup air requirements for Type I clothes dryers are located in Chapter 5. Chapter 7 provides acceptable methods for supplying satisfactory combustion air to ensure proper combustion. Combustion air can be supplied by using indoor combustion air or by introducing the air from the outdoors.
Combustion is the rapid oxidation of fuel to release energy. The oxygen required to release the energy from the fuel normally comes from the air. Incomplete combustion of fuel occurs when inadequate oxygen is provided to the appliance. Combustion is needed to provide ventilation cooling for the casing and internal controls. When a lack of oxygen occurs, some of the carbon is not oxidized, and carbon monoxide forms.
Chapter 8 Chimneys and Vents. Chapter 8 regulates the installation, design, and construction of venting systems for fuel-burning appliances. The provisions addressed within this chapter follow procedures an installer would use to design or evaluate a venting system. Many requirements apply to the design and construction of venting systems, chimneys, installation of gas vents, and the sizing of venting system for a Category I appliance. Sizing venting systems require rigorous engineering calculations. However, the venting sizing requirements and sizing tables in this chapter already perform the calculations for the benefit of the end user.
Combustion appliances produce products of incomplete combustion, including potentially harmful carbon monoxide (CO). It is desirable to vent these products to the outdoors. Although the gas is clean-burning fuel, the products of combustion must not be allowed to collect within a building.
Chapter 9 Installation of Specific Appliances. Chapter 9 regulates the minimum requirements for the design, construction and installation of specific appliances. The provisions address the minimum requirements for gas-fired appliances, oil-fired appliances, wood-fired appliances, and electric-type appliances. In addition to the requirements of this chapter, appliances are also required to comply with the general requirements of Chapter 3.
Chapter 10 Boilers and Pressure Vessels. Chapter 10 regulates the construction, installation, operation, repair, and alteration of boilers and pressure vessels. The safety provisions within this chapter address controls and limit devices for automatic boilers, methods of determining expansion tank capacities, discharge piping, relief valves, shutoff valves, gas-pressure and combustion regulators, and inspections and tests. Potable water heaters are free from the requirements of Chapter 10 as they are within the scope of the Uniform Plumbing Code (UPC).
Pressure vessels store large amounts of energy and must comply with ASME Boiler and Pressure Vessel Code (BPVC) Section VIII.1. The stored energy must be contained to prevent disastrous failures. Boilers must comply with ASME BPVC Section I, ASME BPVC Section IV, or NFPA 85. Installing a safety relief valve and expansion tank prevents pressures in the tank from exceeding the design threshold.
Chapter 11 Refrigeration. Chapter 11 regulates the design, installation, and construction requirements of refrigeration systems and the installation and construction of cooling towers. Refrigeration is a method used for achieving heat transfer to cool spaces. Refrigerants are the most common medium used to transfer the heat energy from the low-temperature level to the high-temperature level. Table
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FORMAT OF THE UNIFORM MECHANICAL CODE
CHBC § 25.4 High relevance — show source text
For SI units: 1 inch = 25.4 mm, °C = (°F-32)/1.8
FIGURE 511.1.2(1) TYPICAL SECTION OF DUCT-TO-FAN
CONNECTION-BUTT JOINT METHOD
[NFPA 96: FIGURE 8.1.3.2(a)]
For SI units: 1 inch = 25.4 mm, °C = (°F-32)/1.8
FIGURE 511.1.2(2) TYPICAL SECTION OF DUCT-TO-FAN
CONNECTION-OVERLAPPING METHOD
[NFPA 96: FIGURE 8.1.3.2(b)]
and exhaust fans that do not meet this velocity. [NFPA 96:8.2.1.2]
511.2.2 Exhaust-Air Volumes. Exhaust air volumes for hoods shall be of sufficient level to provide for capture and removal of grease-laden cooking vapors. Test data, performance tests acceptable to the Authority Having Jurisdiction, or both shall be displayed, provided on request, or both. [NFPA 96:8.2.2.1, 8.2.2.2] Lower exhaust air volumes shall be permitted during no-load and partial load cooking conditions, provided they are sufficient to capture and remove flue gases and cooking effluent from cooking equipment.
For SI units: 1 inch = 25.4 mm, °C = (°F-32)/1.8)
FIGURE 511.1.2(3) TYPICAL SECTION OF DUCT-TO-FAN
CONNECTION–SEALANT METHOD
[NFPA 96: FIGURE 8.1.3.2(c)]
FIGURE 511.1.2(4) TYPICAL SECTION OF DUCT-TO-FAN CONNECTION-DIRECT
TO FAN INLET CONE METHOD
[NFPA 96: FIGURE 8.1.3.2(d)]
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EXHAUST SYSTEMS
511.2.2.1 Performance Test. A performance test shall be conducted upon completion and before final approval of the installation of a ventilation system serving commercial cooking appliances. The test shall verify the rate of exhaust airflow in accordance with Section 508.5.1.2 through Section 508.5.1.5. The permit holder shall furnish the necessary test equipment and devices required to perform the tests.
[ASHRAE 154:4.7.1]
511.2.2.2 Capture and Containment Test. The permit holder shall verify the capture and containment performance of Type I hoods. A field test shall be conducted with all appliances under the hood at operating temperatures, all the hoods operating at design airflows, and with all sources of replacement air operating at design airflows for the restaurant. Capture and containment shall be verified visually by observing smoke or steam produced by actual cooking operation or by simulating cooking using devices such as smoke candles or smoke puffers. Smoke bombs shall not be used. [ASHRAE 154:4.7.2]
CHBC § 1.11.0. High relevance — show source text
This state agency does not adopt sections identified with the following symbol: The Office of the State Fire Marshal’s adoption of this chapter or individual sections is applicable to structures regulated by other state agencies pursuant to Section 1.11.0.
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CHAPTER 8
CHIMNEYS AND VENTS
801.0 General.
801.1 Applicability. The requirements of this chapter shall govern the venting of fuel-burning appliances.
801.2 Venting of Gas Appliances. Low-heat and medium-heat gas appliances shall be vented in accordance with this chapter. Other gas appliances shall be vented in accordance with NFPA 211 or other applicable standards.
801.3 Appliances Fueled by Other Fuels. Appliances fueled by fuels other than gas shall be vented in accordance with NFPA 211 and the appliance manufacturer’s instructions.
802.0 Venting of Appliances.
802.1 Listing. Type B and Type B-W gas vents shall comply with UL 441, Type L gas vents shall comply with UL 641.
802.1.1 Installation. Listed chimneys and vents shall be installed in accordance with this chapter and the manufacturer’s installation instructions. [NFPA 54:12.2.1]
802.1.2 Prohibited Discharge. Appliance vents shall not discharge into a space enclosed by screens having openings less than [1] ⁄ 4 of an inch (6.4 mm) mesh.
802.2 Connection to Venting Systems. Except as permitted in Section 802.2.1 through Section 802.2.7, all appliances shall be connected to venting systems. [NFPA 54:12.3.1]
802.2.1 Appliances Not Required to be Vented. The following appliances shall not be required to be vented:
(1) Listed ranges.
(2) Built-in domestic cooking units listed and marked for optional venting.
(3) Listed hot plates.
(4) Listed Type 1 clothes dryers exhausted in accordance with Section 504.4.
(5) A single listed booster-type (automatic instantaneous) water heater, when designed and used solely for the sanitizing rinse requirements of a dishwashing machine, provided that the appliance is installed with the draft hood in place and unaltered, if a draft hood is required, in a commercial kitchen having a mechanical exhaust system. [Where installed in this manner, the draft hood outlet shall not be less than 36 inches (914 mm) vertically and 6 inches (152 mm) horizontally from any surface other than the appliance.]
(6) Listed refrigerators.
(7) Counter appliances.
(8) Room heaters listed for unvented use.
(9) Direct gas-fired makeup-air heaters.
(10)Other appliances listed for unvented use and not provided with flue collars.
(11)Specialized appliances of limited input such as laboratory burners or gas lights. [NFPA 54:12.3.2]
CHBC § 1.11.0. High relevance — show source text
Adopting Agency BSC BSC-
CGSFM HCD Col6 Col7 DSA Col9 Col10 OSHPD Col12 Col13 Col14 Col15 Col16 Col17 BSCC DPH AGR DWR CEC CA SL SLC Adopting Agency BSC BSC-
CGSFM 1 2 1-AC AC ** SS** ** SS/CC** 1 1R 2 3 4 5 6 6 6 6 6 6 6 6 6 Adopt Entire Chapter X X X X X X X X X X X X Adopt Entire Chapter as
amended (amended sections
listed below)Adopt only those sections
that are listed belowChapter/Section This state agency does not adopt sections identified with the following symbol: The Office of the State Fire Marshal’s adoption of this chapter or individual sections is applicable to structures regulated by other state agencies pursuant to Section 1.11.0.
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CHAPTER 8
CHIMNEYS AND VENTS
801.0 General.
801.1 Applicability. The requirements of this chapter shall govern the venting of fuel-burning appliances.
801.2 Venting of Gas Appliances. Low-heat and medium-heat gas appliances shall be vented in accordance with this chapter. Other gas appliances shall be vented in accordance with NFPA 211 or other applicable standards.
801.3 Appliances Fueled by Other Fuels. Appliances fueled by fuels other than gas shall be vented in accordance with NFPA 211 and the appliance manufacturer’s instructions.
802.0 Venting of Appliances.
802.1 Listing. Type B and Type B-W gas vents shall comply with UL 441, Type L gas vents shall comply with UL 641.
802.1.1 Installation. Listed chimneys and vents shall be installed in accordance with this chapter and the manufacturer’s installation instructions. [NFPA 54:12.2.1]
CHBC § 8-1 High relevance — show source text
CHAPTER 8 INTERIOR FINISHES. . . . . . . . . . . . . . . . . . . . . .8-1
801 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-3
802 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-3
803 Wall and Ceiling Finishes . . . . . . . . . . . . . . . . . . . . . . . . 8-3
804 Interior Floor Finish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-6
805 Combustible Materials in Types I and II Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-7
806 Decorative Materials and Trim . . . . . . . . . . . . . . . . . . . 8-7
807 Insulation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-8
808 Acoustical Ceiling Systems . . . . . . . . . . . . . . . . . . . . . . 8-8
CHAPTER 9 FIRE PROTECTION AND LIFE
SAFETY SYSTEMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-1
901 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-7
902 Fire Pump and Riser Room Size . . . . . . . . . . . . . . . . . . 9-7
903 Automatic Sprinkler Systems . . . . . . . . . . . . . . . . . . . . 9-8
904 Alternative Automatic Fire-Extinguishing Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-17
905 Standpipe Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-20
906 Portable Fire Extinguishers . . . . . . . . . . . . . . . . . . . . . 9-22
907 Fire Alarm and Detection Systems . . . . . . . . . . . . . . . 9-25
908 Emergency Alarm Systems . . . . . . . . . . . . . . . . . . . . . 9-43
909 Smoke Control Systems . . . . . . . . . . . . . . . . . . . . . . . . 9-43
910 Smoke and Heat Removal . . . . . . . . . . . . . . . . . . . . . . 9-51
CHBC § 803.0. High relevance — show source text
(1) Those listed in Section 803.0.
(2) The effective areas of the vent connector and chimney flue of a venting system serving a single appliance with a draft hood shall be not less than the area
of the appliance flue collar or draft hood outlet or greater than seven times the draft hood outlet area.
(3) The effective area of the chimney flue of a venting system serving two appliances with draft hoods shall be not less than the area of the larger draft hood outlet plus 50 percent of the area of the smaller draft hood outlet or greater than seven times the smaller draft hood outlet area.
(4) Chimney venting systems using mechanical draft shall be sized in accordance with engineering methods.
(5) Other engineering methods. [NFPA 54:12.6.3.1]
2025 CALIFORNIA MECHANICAL CODE 155
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CHIMNEYS AND VENTS
FIGURE 802.5.4
TYPICAL TERMINATION LOCATIONS FOR
CHIMNEYS AND SINGLE-WALL METAL PIPES SERVING
RESIDENTIAL-TYPE AND LOW-HEAT APPLIANCE
[NFPA 54: FIGURE A.12.6.2.1]
802.5.6 Inspection of Chimneys or Vents. This inspection shall be made after chimneys, vents, or parts thereof, authorized by the permit, have been installed and before such vent or part thereof has been covered or concealed.
802.5.7 Inspection of Chimneys. Before replacing an existing appliance or connecting a vent connector to a chimney, the chimney passageway shall be examined to ascertain that it is clear and free of obstructions and shall be cleaned if previously used for venting solid- or liquid-fuel-burning appliances or fireplaces. [NFPA 54:12.6.4.1] 802.5.7.1 Standard. Chimneys shall be lined in accordance with NFPA 211. [NFPA 54:12.6.4.2]
802.5.7.2 Cleanouts. Cleanouts shall be examined and where they do not remain tightly closed when not in use, they shall be repaired or replaced. [NFPA 54:12.6.4.3] 802.5.7.3 Existing Chimney. When inspection reveals that an existing chimney is not safe for the intended application, it shall be repaired, rebuilt, lined, relined, or replaced with a vent or chimney to conform to NFPA 211 and shall be suitable for the appliances to be attached. [NFPA 54:12.6.4.4] 802.5.8 Chimney Serving Appliances Burning Other Fuels. An appliance shall not be connected to a chimney flue serving a separate appliance designed to burn solid fuel. [NFPA 54:12.6.5.1] 802.5.8.1 Gas and Liquid Fuel-Burning Appliances. Where one chimney serves gas appliances and liquid fuel-burning appliances, the appliances shall be connected through separate openings or connected through a single opening where joined by a suitable fitting located as close as practical to the chimney. Where two or more openings are provided into one chimney flue, they shall be at different levels.
CHBC § 101.0 High relevance — show source text
2025 CALIFORNIA PLUMBING CODE 487
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488 2025 CALIFORNIA PLUMBING CODE
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APPENDIX J
COMBINATION OF INDOOR AND OUTDOOR COMBUSTION AND
VENTILATION OPENING DESIGN
The provisions contained in this appendix are not mandatory unless specifically adopted by a state agency, or referenced in the adopting ordinance.
J 101.0 General.
J 101.1 Applicability. This appendix provides general guidelines for the sizing of combination indoor and outdoor combustion and ventilation air openings. J 101.2 Example of Combination Indoor and Outdoor Combustion Air Opening Design. Determine the required combination of indoor and outdoor combustion air opening sizes for the following appliance installation example.
Example Installation: A fan-assisted furnace and a drafthood-equipped water heater with the following inputs are located in a 15 foot by 30 foot (4572 mm by 9144 mm) basement with an 8 foot (2438 mm) ceiling. No additional indoor spaces can be used to help meet the appliance combustion air needs.
Fan-Assisted Furnace Input: 100 000 British thermal units per hour (Btu/h) (29 kW)
Draft Hood-Equipped Water Heater Input: 40 000 Btu/h (11.7 kW)
Solution:
(1) Determine the total available room volume. Appliance room volume:
15 feet by 30 feet (4572 mm by 9144 mm) with an 8 foot (2438 mm) ceiling = 3600 cubic feet (101.94 m [3] )
(2) Determine the total required volume. The standard method to determine combustion air is used to calculate the required volume. The combined input for the appliances located in the basement is calculated as follows:
100 000 Btu/h (29 kW) + 40 000 Btu/h (11.7 kW) = 140 000 Btu/h (41 kW)
The standard method requires that the required volume be determined based on 50 cubic feet per 1000 Btu/h (4.83 m [3] /kW). Using Table J 101.2, the required volume for a 140 000 Btu/h (41 kW) combined input is 7000 cubic feet (198.22 m [3] ).
Conclusion: The indoor volume is insufficient to supply combustion air since the total of 3600 cubic feet (101.94 m [3] ) does not meet the required volume of 7000 cubic feet (198.22 m [3] ). Therefore, additional combustion air shall be provided from the outdoors.
(3) Determine ratio of the available volume to the required
volume: Col2 3600 cubic feet = 0.51 7000 cubic feet 7000 cubic feet (4) Determine the reduction factor to be used to reduce the full outdoor air opening size to the minimum required based on the ratio of indoor spaces:
1.00 – 0.51 (from Step 3) = 0.49
(5) Determine the single outdoor combustion air opening size as though all combustion air is to come from outdoors. In this example, the combustion air opening directly communicates with the outdoors:
CHBC § 8-8 High relevance — show source text
CHAPTER 8-8 ARCHAIC MATERIALS AND METHODS OF
CONSTRUCTION . . . . . . . . . . . . . . . . . . . . . . . 15
Section
8-801 Purpose, Intent and Scope . . . . . . . . . . . . . . . . . . . . . . 15 8-802 General Engineering Approaches. . . . . . . . . . . . . . . . . 15 8-803 Nonstructural Archaic Materials. . . . . . . . . . . . . . . . . . 15
8-804 Allowable Conditions for Specific Materials . . . . . . . 15 8-805 Masonry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 8-806 Adobe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
8-807 Wood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
8-808 Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
8-809 Steel and Iron . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
8-810 Hollow Clay Tile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
8-811 Veneers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
8-812 Glass and Glazing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
CHAPTER 8-9 MECHANICAL, PLUMBING AND ELECTRICAL REQUIREMENTS . . . . . . . . . . . . . . . . . . . . . . . 19
Section
8-901 Purpose, Intent and Scope . . . . . . . . . . . . . . . . . . . . . . 19 8-902 Mechanical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
8-903 Plumbing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 8-904 Electrical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
CHAPTER 8-10 QUALIFIED HISTORICAL DISTRICTS,
SITES AND OPEN SPACES . . . . . . . . . . . . . . . 23
Section
CHBC § 1.859 High relevance — show source text
78|–|1.859|0.463| |35.31|–|2.247|0.559| |38.84|–|2.667|0.663| |42.37|–|3.121|0.775| |45.90|–|3.607|0.895| |49.43|–|4.125|1.022| |52.97|–|–|1.157| |56.50|–|–|1.299| |60.03|–|–|1.449| |63.56|–|–|1.607| |67.09|–|–|1.772| |70.62|–|–|1.944| |81.21|–|–|2.503| |91.81|–|–|3.127| |102.40|–|–|3.813|
For SI units: 1 standard cubic foot per minute = 28.32 SLPM, 1 inch = 25 mm, 1 foot = 304.8 mm, 1 pound-force per square inch = 6.8947 kPa
Notes: 1 Based on pressure of 14.7 psig (101 kPa) at 68°F (20°C). 2 Based on pressure of 55 psig (379 kPa) at 68°F (20 °C).
2025 CALIFORNIA PLUMBING CODE 291
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HEALTH CARE FACILITIES AND MEDICAL GAS AND MEDICAL VACUUM SYSTEMS
TABLE 1323.1.4(5) PRESSURE LOSS FOR VACUUM (continued)
FLOW
RATE
(SCFM)1VACUUM LOSS (inch of mercury)
PER 100 FEET FOR COPPER TUBE2Col3 Col4 Col5 Col6 FLOW
RATE
(SCFM)13⁄4 INCH
TUBE1 INCH
TUBE11⁄4 INCH
TUBE11⁄2 INCH
TUBE2 INCH
TUBE49.43 – – – 3.645 0.956 52.97 – – – 4.122 1.081 56.50 – – – 4.626 1.212 63.56 – – – – 1.495 70.62 – – – – 1.803 77.68 – – – – 2.138 84.74 – – – – 2.497 91.81 – – – – 2.882 98.87 – – – – 3.291 105.93 – – – – 3.724 112.99 – – – – 4.181
Frequently asked questions
Can I keep an old masonry chimney and use it for a new gas water heater?
Yes — CHBC allows masonry chimneys to remain in use only if the chimney flue, masonry and grout are evaluated and documented to be in good condition ( § 8-902.6.2 ). If you cannot provide that documentation, the chimney must be repaired, lined, or replaced.
Does the CHBC give the opening sizes I must make for combustion air?
No — CHBC requires a sufficient supply of combustion air ( § 8-902.5 ) but does not publish the numeric sizing rules. For numeric methods and sizing tables, follow the regular California Mechanical/Plumbing Code and appliance manufacturer instructions; CHBC intends that the regular code be used unless the CHBC modifies it.
Are terra cotta chimneys allowed to stay in place?
Not automatically. CHBC § 8-902.6.2 says terra cotta chimneys and Type C metallic vents installed in concealed spaces shall not remain in use unless mitigated and approved on a case‑by‑case basis. Get an approved mitigation plan from the enforcing agency.
What can the enforcing agency require if my historic venting doesn’t meet modern rules?
The enforcing agency may require operational testing of combustion air and venting systems that do not comply with the regular code ( §§ 8-902.5.2, 8-902.6.3 ), and may approve alternatives that achieve equivalent life safety ( § 8-902.1.3 ).
If my room volume is insufficient, what practical options meet the CHBC requirement?
Provide outdoor combustion‑air openings or mechanical makeup air sized per the regular code, install listed direct‑vent appliances, or relocate appliances to a compliant location. CHBC requires sufficiency but expects you to use regular‑code methods for sizing.
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